Carpal tunnel syndrome occurs when the median nerve is squeezed where it passes through the carpal tunnel, thereby causing insanguination of the nerve, which leads to numbness, a cold feeling, and/or pain in the hand and fingers. The carpal tunnel is an anatomic passageway at the base of the wrist through which the median nerve and the flexor tendons for the fingers of the hand pass. It is defined by the carpal bones of the hand and the transverse carpal ligament. Carpal tunnel syndrome is commonly caused by highly repetitive hand motions over a number of years. For instance, carpal tunnel syndrome is common in certain professionals such as secretaries and other professionals who type on a keyboard regularly, carpenters, dentists or anyone who performs the same hand motions repeatedly and regularly.
The current standard of care for alleviating carpal tunnel syndrome is to incise the transverse carpal ligament to open up the carpal tunnel and release the pressure on the median nerve. With few exceptions, most people can manage daily activities with a severed transverse carpal ligament with almost no adverse effects.
The particular current procedure for carpal tunnel release is an endoscopic or arthroscopic procedure in which an incision is made in the wrist proximal of the carpal tunnel. An endoscope with a camera is inserted into the incision and through the carpal tunnel to allow the surgeon to visualize the carpal tunnel, and, particularly, the transverse carpal ligament, and then a knife is inserted alongside the endoscope to cut the transverse carpal ligament.
Referring to FIG. 1, one system available on the market today is the SEG-Way system offered by Core Essence Orthopedics, Inc. of Fort Washington, Pa., USA. The SEG-Way system comprises, among other things, a guide 10 and a retrograde knife 12. As seen in FIG. 1, the guide 10 compromises a longitudinal member 14, containing a channel 16. The channel 16 is for receiving the endoscope 20 and the knife 12 side-by-side. A key feature of the SEG-Way system is that the endoscope and knife are entirely independently manipulable. The guide further comprises a transverse member 19 at its proximal end comprising two wings 21 and 22 extending in opposition transverse directions from the proximal end 23 of the longitudinal member 14. The wings 21, 22 provide a place for the surgeon to hold the guide as well as some stability against rotation about the longitudinal axis 24 of the longitudinal member because the wings essentially rest upon the forearm 26 of the person after the guide has been inserted through the incision 25.
In use, the incision 25 is made in the wrist proximal to the carpal tunnel 27 and the longitudinal member 14 of the guide 10 is advanced distally into and through the carpal tunnel, thereby dilating the carpal tunnel. Once the guide 10 is fully inserted and through the carpal tunnel 27, the endoscope 20 is advanced through the first channel 16 to allow the surgeon to see the carpal tunnel, and particularly, the transverse carpal ligament 30. Then, the knife 12 is advanced distally within the channel 16. As can be seen in FIG. 1, the knife comprises a handle 34 and a distal segment 36 disposed at an angle 38 to each other and has a hooked, retrograde blade 29 at the distal end of the distal segment 36 that faces proximally and cuts when the knife is pulled back in the proximal direction. The angled junction 38 between the handle 34 and the distal segment 36 of the knife 12 generally defines a pivot point about which the knife will be rotated after insertion and prior to cutting. More particularly, the knife 12 is inserted into the channel 16 with the distal segment 36 lying flat in the channel 16 and flush against the bottom of the channel with the blade 29 concealed inside the channel 16 until it is past the transverse carpal ligament so as not to contact any anatomy. This inherently means that the handle segment 34 will be angled upwardly. Then, the surgeon pushes down on the handle to cause the distal segment, and particularly, the retrograde blade to rise up out of the channel 16 so that it can engage the distal edge 30a of the transverse carpal ligament 30 and cut it by drawing the knife 12 back in the proximal direction.